Friday, July 30, 2010

On July 30, 1979, a massive hailstorm struck Ft. Collins, Colorado, producing baseball to grapefruit size hail for over 30 minutes. This storm caused what, to date, had only been the 2nd death ever recorded in U.S. History from a hailstone. To make that statistic even worse, the victim was a 3 month old baby, who died when a hailstone struck the child in the head as his mother was attempting to rush him to safety.

The image above is a long-distance shot of the thunderstorm responsible for producing the devastation of that day. Twenty-five people were injured and over 3,000 automobiles severely damaged from this storm, not to mention the other property damage that was widespread across the city.

I've been pleasantly surprised by the number of e-mails I've received this week asking why I haven't been making a daily post. My apologies ... my "real" job has kept me hopping this week well into the evening hours where I would normally take some time, collect my weather-related thoughts & make a post.

I promise I'll be back on the job this weekend...we've got lots to talk about from "what the heck has been going on in the tropics" to a record setting hailstorm in the Dakotas...so stay tuned!

Monday, July 26, 2010

The Hydrometeorological Prediction Center (or HPC) is one of 9 service centers under the umbrella of the National Centers For Environmental Prediction (NCEP) which is part of the National Weather Service (NWS), which is part of the National Oceanic and Atmospheric Administration (NOAA). Tired yet?

The center is currently housed in the "World Weather Building" in Camp Springs, Maryland. A brand new facility is under construction on the University of Maryland campus in College Park. Completion date is unknown as of the time of this writing.

The HPC is primarily responsible for housing the super computers that run and produce the major global weather forecast models (this would be considered the "numerical weather prediction" side of the house).

The HPC also produces several of the more "operational" forecast and guidance products, such as the Quantitative Precipitation Forecast (QPF) (a forecast of surface rainfall amounts),

as well as medium and long range (i.e,. 3 to 7 day) forecast maps

as well as excessive snow and/or ice forecasts, etc. The HPC also takes over for the National Hurricane Center when that office ceases to issue advisories on a tropical system that has made landfall and loses tropical characteristics.

In a nutshell, I guess you could say the HPC is the support center for all of the local NWS forecast offices, as well as the private sector and media interests that are focused on weather information, forecasting & warning operations. All of the various weather observations and other data from around the nation and globe flows through the center, is processed by both supercomputers and human forecasters and is output in various forms to the end users.

Sunday, July 25, 2010

The Storm Prediction Center (or SPC) is the branch of the National Weather Service (NWS) charged with issuing timely and accurate forecasts pertaining to severe thunderstorms, tornadoes and other small scale severe weather phenomena.

While severe thunderstorms and tornadoes are the most common things that come to mind when we talk about the SPC, they also provide forecasts and other guidance concerning severe winter weather hazards, heavy rainfall and flash flooding, and even fire weather hazards.

For most of the last 50 years the unit was housed in the Federal Building in Kansas City, MO. In 1997 the unit was moved to Norman, OK and was housed inside the National Severe Storms Laboratory. Its most recent move in September 2006 was to the brand new, state of the art National Weather Center building on the University of Oklahoma campus (shown in the image above).

The National Hurricane Center (NHC), also known as the Tropical Prediction Center or TPC, is the division of the National Weather Service charged with monitoring the tropics and forecasting the development of tropical cyclones (i.e., tropical depressions, storms or hurricanes).

The bunker-like structure housing the NHC is located on the Florida International University campus in Miami, FL. The building was specially designed to withstand a direct hit by a hurricane (inspired by the damage caused to the center's former location by Hurricane Andrew in 1992).

Below are some images of the inside of the center's forecast and operations areas:

The official website is located here. A virtual tour of the office is available here.

Saturday, July 24, 2010

As we forecast in a post earlier this morning, Bonnie has diminished into an area of low pressure over the northcentral Gulf of Mexico. Only scattered thunderstorms and brief, gusty winds are to be expected across the region as the system moves toward the Northwest.

The above satellite image shows Tropical Depression Bonnie as she continues Northwest across the northern Gulf of Mexico this morning. The system has continued to disorganize overnight, and is now just barely even a Tropical Depression this morning.

The official National Hurricane Center track and forecast map is below. They are still forecasting Bonnie to become a Tropical Storm again before reaching the Louisiana coast late this evening/tonight. However, if the current weakning and disorganizing trend continues, Bonnie is likely to be reduced to just a trough of low pressure later on today. This trend is indeed forecast by most of the major computer models at this time.

This is obviously good news not only for the oil spill area, but also for the folks that would have been impacted by a potentially stronger system when making landfall.

Ahhh....but the tropical season is young. Coastal residents know that the danger is only just beginning....and we're not out of the woods until October!

Friday, July 23, 2010

The center of Tropical Storm Bonnie crossed into the Biscayne Bay of Florida around 10am Central Time this morning. The system has become very disorganized overnight and into this morning, and is now only a marginal Tropical Storm. Heavy rains and gusty winds are the greatest threats as the system traverses the Florida peninsula today. It is currently moving West/Northwest at almost 20 mph, a rather fast pace for a tropical system.

Many of the computer forecast models today are forecasting Bonnie to weaken, with some even forecasting a total loss of tropical characteristics as she emerges back out into the Gulf of Mexico later tonight. The latest National Hurricane Center forecast track is below:

As you can see, the NHC is currently forecasting Bonnie to remain a Tropical Storm as she emerges back out into the gulf later today/tonight. We'll have to see how the system holds-up over Florida today. Right now, it looks to me like further weakening is likely, mainly due to the fact that such systems don't do well over land (loss of warm water, etc.), and she was rather disorganized when entering the peninsula to begin with.

Thursday, July 22, 2010

Just as we expected this morning, the tropical wave to the Southeast of Florida was upgraded first to Tropical Depression 3 before Noon, then Tropical Storm Bonnie later in the afternoon. This system is moving West/Northwest and is expected to continue on a general Northwesterly track for the next few days.

Below are the computer model forecast tracks, as of 1pm Central Time today. Keep in mind the system was still "Tropical Depression 3" at the time the image was produced:

The National Hurricane Center is generally keeping with the middle of the above foreacast model tracks. Below is their latest forecast track map:

The letter "S" in the center of the black forecast point dots along the forecast track in the image above indicate that the Hurricane Center, and all of the forecast models so far, expect Bonnie to remain at Tropical Storm strength. She is not currently forecast to reach hurricane strength.

Even as a Tropical Storm, some serious problems are likely to occur in parts of Florida on Friday, and will also cause problems in the Gulf oil spill area over the weekend.

The tropics have continued to "heat up" over the last few days. A couple of days ago I created a post on "Invest 97L", which is soon to become either a Tropical Depression, or perhaps go right into named Tropical Storm Bonnie. This system is currently located in the Southeast Bahamas (noted by the red circle in the image above). The National Hurricane Center is forecasting a 100% chance of this system becoming a tropical depression or storm in the next 48 hours. In my opinion, based on satellite imagery and available surface observations, the system has already reached depression status. I would expect an "upgrade" on the classification of this system later this morning. Folks in Florida and the Eastern Gulf of Mexico should watch this system closely over the coming days. I'll post the latest computer model forecast guidance on this system later today after the morning computer models process the latest data.

The second area of interest, noted by the orange circle on the above image (in the extreme Southwest Gulf of Mexico), is a strong tropical disturbance advancing slowly westward toward Mexico. This system also has a chance of becoming at least a tropical depression before moving into Mexico on Friday. The National Hurricane Center currently places that probability at 50%.

The above is a satellite image of "Tropical Invest 97", a strong tropical wave located near Hispaniola. This disturbance is becoming better organized as it drifts slowly toward the West/Northwest. The "60%" notation to the upper left corner of the system denotes the probability, as forecast by the National Hurricane Center, of the system becoming a tropical depression, storm or hurricane within the next 48 hours.

Below is an image depicting the latest computer model forecasts as to where this system is likely to track:

As you can see, the consensus is for the system to track generally Northwest out into the Eastern Gulf of Mexico toward the end of the week (each point on the forecast track image represents a 12-hour period of time).

We'll have to closely monitor this system, not only for its potential impact on life and property along the central and eastern Gulf Coast, but also for potential impact on the oil spill situation in the northern Gulf.

Sunday, July 18, 2010

The above image (click to enlarge) shows the swath of large hail, high wind and tornado reports from central through southeast Minnesota from yesterday evening. Several tornado reports were received, though initial reports show that they were not as damaging (nor deadly) as the events of mid-June this year (thankfully).

Many of the same storms congealed into a complex of thunderstorms that continues to roll Southeast across Missouri and Illinois this morning. Below is the St. Louis, MO radar image taken about an hour ago as the complex rolled through the metropolitan area (near center of image). Several reports of wind damage have been received.

Sunday, July 11, 2010

The above image was taken from the Little Rock, AR (KLZK) doppler radar about 10 minutes ago. This is a "reflectivity" image, which means it's displaying energy reflected back to the radar by rain, hail, etc. Seasoned readers will immediately notice the impressive "hook echo" signature on this storm which was located about 20 miles East of Little Rock at the time. Such a signature is a "classic" indicator of rotation and tornado potential in a severe thunerstorm. This is more of a spring type signature that you'd expect to see on a storm in April or early May, not July!

The image below was taken by the same radar shortly before the above image, only this time in "storm relative velocity" mode, which shows the wind motion within the storm relative to the radar's position & the storm's movement. The green colors show wind blowing toward the radar, while the red colors show wind blowing away from the radar. The radar is located near the upper left corner of the screen (at the blue "KLZK" lettering).

Can you pick out the strong rotation Southeast of Lonoke? If not, take a peak at the next image, where I've noted it for you:

With all of the hype about what an active tropical season we're in for, you might find yourself wondering - Tropical What??? lately. After 2 systems moved through the Gulf in roughly one week (Alex and Tropical Depression 2), it's been relatively quiet for the past few days across the Atlantic Basin.

The above image shows the Sea Surface Temperature (or SST) situation as of late Friday afternoon. The upper image is the observed temperature, and the lower image shows the change in temperature over the previous 5 days. As you can see, Alex and Tropical Depression 2 have taken a toll on the SSTs in the western Gulf of Mexico (note the lighter blue shades on the lower image depicting a decrease in SST over that area).

As a general rule of thumb, tropical systems tend to develop and/or intensify in regions where the SST is (1). warm to begin with and (2) rising. With this in mind, areas of decreasing SST would tend to be less likely to see organized tropical development and/or intensification in the near-term. On the other hand, areas where SSTs are rising would tend to be more favorable for tropical development.

Meanwhile, take a look at the SST change off the coast of west/northwest Africa. A pronounced warming has taken place over the past 5 days in that region. The image below (courtesy of stormpulse.com) shows an impressive looking tropical wave moving off of the African coast at this time. It will be interesting to see if this system taps the increasingly warm, unstable conditions in the region and is able to develop into an organized system.

Friday, July 9, 2010

Call me old fashioned, but I fully expect it to be hot outside on a July afternoon. I've lived in the southern U.S. my entire life. If it weren't 95 degrees with a heat index of 105 every afternoon from June through September I would fear that I had been abducted by Siberian aliens. That's what pools, rootbeer floats, popsicles, water balloon fights and air conditioners are for!

I can't help but be amused by the news media freaking out this past week over 95+ degree weather in the Northeast. Last time I checked it was summertime up there, too. Call me an idiot, but as a result, I would expect it to be hot every now and then, even in New York City...

Don't get me wrong. It's absolutely horrible to hear of anyone actually dying from heat exhaustion in their own home. Many times this involves the elderly and/or folks with serious illnesses. Here in Texas and around the country there are many organizations, like Family Eldercare, who will help folks in need with free fans.

If you know an elderly person or someone in poor health who is without air conditioning in their home, help them find an agency in their area that can provide assistance during the hot summer months. Better yet, take them to a movie, or the library during the hottest part of the day. I bet even Wal-Mart would let you wander around in air conditioned comfort - and they might just sell something to you, too.

Thursday, July 8, 2010

The tropical disturbance we've been monitoring over the past several days has been deemed a depression (actually was late yesterday evening). The above image shows Tropical Depression 2 over the Western Gulf shortly after 6am this morning. As of 7am central time, the center of the depression was about 80 miles East of Brownsville, TX.

It is currently moving to the Northwest at about 15 mph, and the track forecast from the National Hurricane Center is shown below:

Though still recovering from Alex, which took a very similar track last week, the waters over this portion of the Gulf are still very warm, and some further intensification is possible. A Tropical Storm Warning has been issued for a small portion of the Mexican and Texas coasts, and the depression may strengthen to a minimal Tropical Storm Bonnie before making landfall. As I blogged yesterday evening, the main threat from this system will be heavy rain.

Many areas of southeast Texas and northern Mexico are still trying to dry out from Alex last week, and the Rio Grande River is still flooding many areas, as well as smaller streams across the region. This could be a very dangerous situation today into Friday as additional heavy rains fall over many of the same areas. Below is the latest precipitation forecast for today:

As you can see, widespread amounts of 2-4 inches of rain are forecast across much of central and east Texas. Localized amounts of 4-6 inches are likely in southeast and southcentral Texas. This threat will spread West with time into Friday.

Wednesday, July 7, 2010

The above image is a satellite picture taken a short while ago of a disturbance located in the western Gulf of Mexico (click the image to enlarge it). This is the same system I've been blogging about for the past several days. The 50% notation to the right is the Tropical Prediction Center (aka National Hurricane Center) forecast of the probability of the system becoming at least a Tropical Depression before making landfall over the next 48 hours.

As I remarked in my last post on this system, it was less organized when compared to Alex before reaching the Yucatan Peninsula, which seems to have taken a toll on its ability to strengthen. While that's obviously good news as far as high wind potential is concerned, it will still produce widespread, heavy rain across much of the same areas hit hard by Alex last week. This will result in a significant flooding threat across portions of Eastern Mexico and Texas initially, then spreading Northeast into the central Plains through the weekend.

The image below depicts the HPC forecast rainfall amounts over the coming 5 days. As you can see, widespread amounts of 4+ inches are forecast from parts of central Texas into southeast Oklahoma and northwest Arkansas, with widespread 1-4 inch rainfall totals forecast on either side of those areas.

As I've said before, we can't look a gift horse in the mouth rainfall-wise during the otherwise hot and dry summer months, but folks in already rain-soaked areas need to stay alert and be prepared to move to higher ground if in a flood-proned area.

The above image depicts the latest computer model guidance as to the eventual track of this system. Residents of Mexico & Texas (same areas where Alex hit last week) stay alert for the next 24-36 hours as this system approaches. We'll be able to identify any significant wind threat during the day on Thursday, but at this time it appears to be a "toad choker" situation unfolding as described above.

Monday, July 5, 2010

The above image is the Lake Charles, LA (KLCH) WSR-88D in reflectivity mode, taken a few moments ago. The swirling configuration you see at the center of the image, just offshore of Franklin and Terrebonne Parishes in Louisiana, is the center of "Tropical Invest 95". The system was moving almost directly North/Northwest earlier in the evening, but has recently turned more toward the West/Northwest. So far this evening, surface and buoy observations have not indicated any sustained winds of tropical depression or storm strength (although there have been some gusts of depression strength). As long as the center of circulation remains over warm Gulf waters, all bets are off; however, the close proximity to land will limit the potential of any significant development tonight before the system finally moves onshore in southern Louisiana.

Meanwhile, "Tropical Invest 96" continues to churn immediately to the East of the Yucatan Peninsula this evening. Below are the latest computer forecast model solutions as to where this system will move during the week. The consensus continues to point toward the Texas coast. Stay tuned....

The above infrared satellite image was taken about 30 minutes ago, and depicts the area of disturbed weather (thus far identified as "Tropical Invest 96") that I've been blogging about over the past several days, in the Western Carribean.

[Before I go any further, I'd like to take care of some "housekeeping" type business. I guess I've always taken for granted that everyone knows that they can "click" on any image that I post in this blog and a larger, hopefully clearer, view will be displayed. I've had a couple of folks ask me the past few days if I could make the images bigger on the blog. Turns out they didn't realize they could click for a larger view. I hope this helps!]

The squiggly (I guess that's a word as the trusty spell checker didn't flag me as a violator) lines spreading Northwest from the center of the disturbance depict the latest track forecasts by the major computer models. As you can see, the consensus has shifted Northward since the last update, with eventual landfall shown along the middle Texas coast late this week. Thus far, the models bring this system up to Tropical Storm strength in the Gulf. As I mentioned in my last post, regardless of tropical storm or hurricane, additional heavy rains could cause siginficant problems across southeast Texas and Mexico should this forecast verify.

One major difference thus far between this system and Alex is that Alex had already become quite organized by this stage. It will be interesting to see how this system holds-up after traversing the Yucatan peninsula over the next 24-36 hours. It may have a harder time reorganizing once it emerges back out into the gulf, compared to what Alex was able to do.

Sunday, July 4, 2010

The visible satellite picture above was taken at 11:45 a.m. Central Time. It shows a couple of tropical waves/disturbances over the Carribean and Atlantic basin. The one toward the lower left corner of the image (to the Southeast of the Yucatan Peninsula of Mexico) is the system that I blogged about a couple of days ago (which had already been picked up by the ECMWF computer models at that time).

The image below is a summary of the current forecast model tracks of this system. As I pointed out in my last post on the subject, the models want to take this system on a strikingly similar (if not identical) track as with recent Hurricane Alex. This trend has not changed thus far, and if anything has been solidified by other computer model forecasts jumping on board with the same conclusion. Obviously a lot can change over the next 5 or 6 days, however we'll have to keep monitoring the system very closely.

The National Hurricane Center has scheduled a hurricane hunter aircraft to fly into this area tomorrow and investigate the system.

Even if this system does not strengthen to hurricane force, the potential for additional heavy rains alone across parts of Mexico & Texas would be of great concern later this week. Stay tuned!

Friday, July 2, 2010

No, the above image isn't a copy of a map from earlier this week showing Hurricane Alex approaching the Mexican coast South of Texas (note the "L" just off the Texas coast on the upper-right portion of the 4-panel image). It is a computer forecast model from this morning produced by the European Center for Medium Range Weather Forecasting (ECMWF for short, thank goodness), and is valid at 7am Central Time this coming Friday, July 9th. Now, keep in mind we're talking 7 full days out into the future, and the system depicted in the image above has not yet even formed in the Carribean Sea as of this writing, but the ECMWF has a pretty solid track record of accurately forecasting tropical systems. It will certainly be interesting to see how this pans out over the coming week.

Meanwhile, beneficial rains continue to fall across much of southern and central Texas thanks to Alex. The image below is of the New Braunfels, TX WSR-88D radar (KEWX), taken just a few moments ago. This image depicts the radar's estimate of rainfall totals across the region since yesterday:

The dark purple areas Southwest of Houston (KHGX) indicate rainfall estimates of 8-10 inches, while the brighter red and orange areas depict rainfall estimates of 3-6 inches. As you can see, widespread estimates of 2-4 inches are observed across much of the remainder of the region.

Texans know to be thankful for any amount of rain we receive during the summer months, but we could have some serious problems across portions of the southeast half of the state if another tropical system moves across the region as predicted by the ECMWF model forecast that I first spoke about. Time will tell....stay tuned!